Centrifugal fan

ABSTRACT

A centrifugal fan includes: a motor; an impeller having an inlet port, the impeller being configured to be rotated by the motor and to discharge air suctioned from the inlet port outward from an outer circumferential portion of the impeller; a lower casing that is located below the impeller; a circuit board disposed between the lower casing and the impeller, the circuit board being, mounted with an electrical component including a drive circuit that drives the motor, wherein the impeller has a recessed portion formed in an annular shape around a rotational axis and on a lower face that faces the lower casing and the circuit hoard, and wherein at least a part of the electrical component is located inside the recessed portion of the impeller.

BACKGROUND

1. Field of the Present Invention

The present invention relates to a centrifugal fan and, more particularly, to a centrifugal fan that discharges air outward from an outer circumferential portion of an impeller with rotation of the impeller.

2. Description of the Related Art (Background of the Invention)

A centrifugal fan is widely used for cooling, ventilafion, air conditioning, and the like in a variety of equipment such as household electrical appliances, OA equipment, and industrial equipment or for a fan in vehicles.

An example of a structure of a centrifugal fan is disclosed in JP-A-2012-189047, in which an impeller is accommodated between an upper casing and a lower casing. Such a centrifugal fan is configured to discharge air suctioned from an inlet port outward with rotation of the impeller from an outlet port formed on a side face between the upper casing and the lower casing.

Recently, a decrease in size of equipment on which the above-mentioned centrifugal fan is mounted has progressed and demands for a centrifugal fan with a smaller thickness have increased.

In the centrifugal fan described in JP-A-2012-189047, the lower casing also serves as a main plate of the impeller, and a motor and a circuit board are accommodated in a recessed portion formed in the lower casing. As a result, the thickness of a part above the lower casing is reduced and the overall thickness of the centrifugal fan is reduced.

However, in the centrifugal fan described in JP-A-2012-189047, a manufacturing cost becomes relatively high. That is, since a gap between a partition wall of the lower casing and the blades has a great influence on air volume characteristics of the centrifugal fan, the gap should be precisely set to an appropriate value. Accordingly, dimensional accuracy of components of the centrifugal fan should be managed with high accuracy, and component costs may increase.

SUMMARY

One of objects of the present invention is to provide a centrifugal fan with a small thickness and a low manufacturing cost.

According to an illustrative embodiment of the present invention, there is provided a centrifugal fan including: a motor; an impeller having an inlet port, the impeller being configured to be rotated by the motor and to discharge air suctioned from the inlet port outward from an outer circumferential portion of the impeller; a lower casing that is located below the impeller; a circuit board disposed between the lower casing and the impeller, the circuit board being mounted with an electrical component including a drive circuit that drives the motor, wherein the impeller has a recessed portion formed in an annular shape around a rotational axis and on a lower face that faces the lower casing and the circuit board, and wherein at least a part of the electrical component is located inside the recessed portion of the impeller.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a plan view illustrating a centrifugal fan according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line A-A shown in FIG. 1;

FIG. 3 is a plan view illustrating an impeller;

FIG. 4 is a perspective view illustrating a bottom surface of the impeller;

FIG. 5 is a partial end-elevational view of an impeller according to a modified example of the embodiment; and

FIG. 6 is a partial end-elevational view of an impeller according to another modified example of the embodiment.

DETAILED DESCRIPTION

Hereinafter, a centrifugal fan according to an embodiment of the present invention will be described.

FIG. 1 is a plan view illustrating a centrifugal fan according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line A-A shown in FIG. 1.

Referring to FIGS. 1 and 2, a centrifugal fan 1 includes a casing 10, an impeller 30, and a motor 60. The centrifugal fan 1 has a rectangular parallelepiped shape having a substantial square shape in a plan view as a whole. The centrifugal fan 1 has a small thickness in which the size in the vertical direction (height) is relatively small.

The impeller 30 is attached to a rotor 61 which rotates along with a shaft 62 of the motor 60. The centrifugal fan 1 rotates the impeller 30 using the motor 60. The centrifugal fan 1 discharges air suctioned from an inlet port 33 to a lateral side of the impeller 30 with the rotation of the impeller 30. That is, air suctioned from the inlet port 33 passes between blades 51 of the impeller 30 and is discharged outward from an outer circumferential portion of the impeller 30, by a hydrodynamic force resulting from a centrifugal action accompanying with the rotation of the impeller 30. The air is discharged outward from outlet ports 19 which are formed on four side faces of the casing 10.

As illustrated in FIG. 2, the casing 10 includes an upper casing 11 and a lower casing 21. The upper casing 11 is disposed above the impeller 30 and the lower casing 21 is disposed below the impeller 30. The upper casing 11 and the lower casing 21 are coupled to each other using fastening members 18 which are tapping screws via supports 17 disposed at four corners in a plan view. The supports 17 are formed by integral molding with the upper casing 11 and the fastening members 18 are tightly fastened to pilot holes formed in the supports 17. A through-hole may be formed in the support 17 and the upper casing 11 and the lower casing 21 may be coupled to each other by inserting a bolt as the fastening member 18 through the through-hole and fixing the bolt with a nut on the other side. The fastening members 18 are not limited to these configurations. The supports 17 may be members which are formed independently of the upper casing 11 or the supports 17 may not be necessarily formed.

The upper casing 11 is formed, for example, a resin such as engineering plastic. An opening 16 is formed at the center of the upper casing 11. The opening 16 has a circular shape in a plan view and air is introduced into the inlet port 33 of the impeller 30 from the opening 16. Plural small-thickness portions 13 are formed on the top surface side of the upper casing 11.

The lower casing 21 is formed of, for example, a metal sheet such as a steel sheet. An accommodating portion 22 which is concave downward from the parts of the lower casing 21 coupled to the supports 17 is formed at the center of the lower casing 21. A part (lower part) of the motor 60 and the circuit board 76 are accommodated in the accommodating portion 22.

A side plate 23 which is bent in a rotation axis direction (hereinafter, simply referred to as an axial direction) of the impeller 30 is disposed in the outer circumferential portion of the lower casing 21. Since the side plate 23 is formed, the rigidity of the lower casing 21 is improved.

In the centrifugal fan 1, areas between the upper casing 11 and the lower casing 21 other than the fastened portions (support portions) of the upper casing 11 and the lower casing 21 in four side portions of the casing 10 serve as the outlet ports 19 of air.

The material of the lower casing 21 is not limited to a metal sheet such as a steel sheet, and may be a resin material.

The motor 60 is, for example, an outer rotor type brushless motor.

A rotor 61 of the motor 60 includes a cup-like rotor yoke 63 which is opened downward, an annular magnet 64 which is attached on the inner circumferential surface of the rotor yoke 63, and a shaft 62 which is attached to the center of the rotor yoke 63.

The shaft 62 is rotatably supported by a pair of bearings 66 and 67 attached to a bearing holder 65. A stator 70 is formed on the outer circumferential portion of the bearing holder 65.

The stator 70 includes a stator core 71, an insulator 72, and a coil 75. The stator core 71 is formed by stacking plural cores each including plural salient poles extending in the outward radial direction from an annular yoke. The insulator 72 has a configuration in which an upper insulator 73 and a lower insulator 74 are attached from both sides in the axial direction of the stator core 71. The coil 75 is wound on the salient portion of the stator core 71 with the insulator 72 interposed therebetween. The bearing holder 65 is inserted into an opening formed at the center of the annular yoke of the stator core 71 and thus the stator 70 is disposed outside the bearing holder 65. The outer circumferential surface of the stator core 71 faces the inner circumferential surface of the magnet 64 with a predetermined air gap in the radial direction (the left-right direction in FIG. 2) therebetween.

The motor 60 is attached to a bottom surface 22 a of the accommodating portion 22 using a fastening member 68 such as a screw or a bolt. The motor 60 is attached to the lower casing 21 by inserting one end of the bearing holder 65 into an opening formed in the bottom surface 22 a of the accommodating portion 22 and tightly fastening the fastening member 68 such as a bolt to the bearing holder 65. A flange 65 a is formed in the lower end portion of the bearing holder 65 and the fastening member 68 is fastened to the flange 65 a. The number of fastening positions of the fastening member 68 is, for example, three, but is not limited to this value. The motor 60 may be attached to the lower casing 21 by fixing the lower portion of the bearing holder 65 to the bottom surface 22 a of the accommodating portion 22 by caulking instead of using the fastening member 68.

The circuit board 76 provided with a drive circuit for driving the motor 60 is attached to the lower insulator 74. A part of the circuit board 76 along with a part of the motor 60 is accommodated in the accommodating portion 22. An electronic component 77, such as an electrical device and a control IC for controlling driving of the motor 60, is mounted on the circuit board 76. Winding ends of the coil 75 are electrically connected to a wiring pattern of the circuit board 76.

The impeller 30 is disposed within the casing 10. The impeller 30 has a disk shape as a whole. The impeller 30 includes an annular shroud 31, a hub 41, a main plate 42, and plural blades 51 disposed between the annular shroud 31 and the main plate 42. The inlet port 33 is formed at the center of the annular shroud 31. The hub 41 attached to the rotor 61 is disposed at the center of the impeller 30. The main plate 42 is connected to the hub 41 and has a disk shape extending in the radial direction from the outer circumferential surface of the hub 41 and being centered on the hub 41.

The rotor yoke 63 of the motor 60 is inserted into the hub 41. The rotor yoke 63 is attached to the impeller 30 by inserting plural bosses 41 a formed in the hub 41 into plural through-holes formed on the top surface of the rotor yoke 63 and heating the tips of the bosses 41 a to caulk the through-holes.

FIG. 3 is a plan view illustrating the impeller 30.

In FIG. 3, the rotation direction of the impeller 30 is indicated by arrow RD.

As illustrated in FIG. 3, the plural blades 51 are arranged regularly at predetermined intervals on a circumference in a plan view. The blades 51 have the same curved shape and are backward-curved blades (so-called turbo blades) which are obliquely curved and inclined backward with respect to the rotation direction. Each blade 51 extends downward in the axial direction from the annular shroud 31 and is coupled to the main plate 42. The shape and the number of blades 51 are not limited to this example.

In this embodiment, the annular shroud 31 and the blades 51 are formed, for example, by integral molding using a resin. The hub 41 and the main plate 42 are formed, for example, by integral molding using a resin. The impeller 30 is formed by joining two members formed by integral molding in this way. The joining is performed as follows. That is, two members are joined by inserting the lower ends of the blades 51 into the recessed portion formed in the main plate 42, inserting pins formed at the lower ends of the blades 51 by integral molding into holes formed in the recessed portion, and heating the tips of the pins to caulking the recessed portion.

FIG. 4 is a perspective view illustrating a bottom surface side of the impeller 30.

As illustrated in FIG. 4, in this embodiment, a recessed portion 45 is formed on the bottom surface (surface facing the lower casing 21) of the main plate 42. The recessed portion 45 is formed in an annular shape around the rotation shaft of the impeller 30. The recessed portion 45 is a groove having a substantially U-shaped cross-section.

As illustrated in FIG. 2, an upper portion of the electronic component 77 mounted on the circuit boar 76 is accommodated in a part of the recessed portion 45. Accordingly, even when the electronic component 77 having a relatively large height is mounted on the circuit board 76, it is possible to dispose the impeller 30 and the circuit board 76 so as to be close to each other while preventing interference (contact) between the impeller 30 and the electronic component 77.

As illustrated in FIG. 3, the diameter D1 of the impeller 30 is greater than the diameter D2 of a circle C2 passing through the outermost circumferential edges of the blades 51. The gap size in the axial direction between the annular shroud 31 and the main plate 42 gradually increases from the position of the outermost circumferential edge of each blade 51 to the outer circumferential edge of the impeller 30 (gradually increases toward the outer circumferential edge of the impeller 30). Accordingly, air guided to the outermost circumferential edges of the blades 51 is smoothly guided so as to spread outward from the impeller 30 and is discharged from the impeller 30 through the outlet ports 19. Therefore, it is possible to suppress noise generated around the outlet ports 19.

In this embodiment, as illustrated in FIG. 2, a part on the outer circumference side of the lower surface of the annular shroud 31 is curved to form a wing upper surface shape. That is, the lower surface on the outer circumference side of the annular shroud 31 has a slowly-curved shape which is convex downward. In other words, the lower surface of the outer circumference side of the annular shroud 31 has a curved shape like a horn (a bell shape (a trumpet shape) of a brass instrument). Accordingly, air flowing outward from the outer circumferential edges of the blades 51 is not easily separated from the surface of the annular shroud 31 and can be more effectively guided and smoothly discharged so as not to cause disturbance of an air flow.

Since the centrifugal fan 1 has the above-mentioned configuration, the following advantages are obtained. That is, a part of the electronic component 77 on the circuit board 76 is accommodated in a part of the recessed portion 45 formed on the bottom surface of the main plate 42 (a part of the annular recessed portion 45 corresponding to a part in which the electronic component 77 is formed). Accordingly, it is possible to avoid interference between the impeller 30 and the electronic component 77 and to dispose the circuit board 76 and the impeller 30 so as to be close to each other. Therefore, it is possible to decrease the thickness of the centrifugal fan 1.

The main plate 42 is disposed below the blades 51, and the centrifugal fan 1 has a structure different from the structure in which the lower casing is also used as the main plate of the impeller in the related art. Accordingly, since the dimensional accuracy (flatness) of the lower casing 21 does not need to be managed with high accuracy and the lower casing 21 can be formed, for example, using press working, it is possible to reduce the manufacturing cost of the centrifugal fan 1.

The impeller 30 includes the main plate 42 and is formed by joining two members. Accordingly, the number of components of the centrifugal fan 1 is greater than that in the structure in which the lower casing is also used as the main plate of the impeller. However, the decrease in cost due to the manufacturing of the lower casing 21 using press working is greater than the increase in cost due to the increase in the number of components and thus it is also possible to decrease the manufacturing cost in this embodiment.

The diameter D1 of the impeller 30 is greater than the diameter D2 of the circle C2 passing through the outermost circumferential edges of the blades 51. The gap size in the axial direction between the annular shroud 31 and the main plate 42 gradually increases from the position of the outermost circumferential edge of each blade 51 to the outer circumferential edge of the impeller 30, and the bottom surface on the outer circumferential edge side of the annular shroud 31 is curved to form a wing upper surface shape. Accordingly, air output from the outer circumferential edges of the blades 51 is smoothly discharged outward along the lower surface of the annular shroud 31, thereby suppressing generation of noise around the outlet ports 19.

In this embodiment, the part on the outer circumferential edge side of the lower surface of the annular shroud 31 is formed in a wing upper surface shape, and the part on the outer circumferential edge side of the upper surface of the main plate 42 is formed in a linear shape (planar shape) in a side cross-sectional view, but the present invention is not limited to these shapes. For example, when the part on the outer circumferential edge side of at least one of the lower surface of the annular shroud 31 and the upper surface of the main plate 42 is curved to form a wing upper surface shape as will be described below, it is possible to achieve an advantage of preventing separation of air discharged from the impeller 30 as described above.

FIG. 5 is a partial end-elevational view of an impeller 130 according to a modified example of this embodiment.

The end elevation illustrated in FIG. 5 shows a modified example of the impeller 30 illustrated in FIG. 2. As illustrated in FIG. 5, the impeller 130 includes an annular shroud 31, blades 51, a hub 41, and a main plate 142 having a shape other than described above. The upper surface on the outer circumference side of the main plate 142 is curved to form a wing upper surface. That is, the lower surface on the outer circumference side of the main plate 142 has a slow-curved shape which is convex upward. Since the parts on the outer circumference side of the lower surface of the annular shroud 31 and the upper surface of the main plate 142 are curved to form a wing upper surface shape in this way, air of the outer circumferential edges of the blades 51 is smoothly discharged from the impeller 130.

FIG. 6 is a partial end-elevational view of an impeller 230 according to another modified example of this embodiment.

The end elevation illustrated in FIG. 6 shows another modified example of the impeller 30 illustrated in FIG. 2. As illustrated in FIG. 6, the impeller 230 includes an annular shroud 231 having a shape other than described above, blades 51, a hub 41, and a main plate 142. The upper surface on the outer circumference side of the annular shroud 231 is curved in a substantially linear shape on a side cross-sectional view, which is different from the above-mentioned shape. The lower surface of the outer circumference side of the main plate 142 is curved to form a wing upper surface and a gap size in the axial direction between the annular shroud 231 and the main plate 142 gradually increases from the position of the outermost circumferential edges of the blades 51 to the outer circumferential edge of the impeller 230. Even when the part on the outer circumferential edge side of the upper surface of the main plate 142 is curved to form a wing upper surface shape in this way, air of the outer circumferential edges of the blades 51 is smoothly discharged from the impeller 230.

The shape of the casing is not limited to the substantially square shape in a plan view. The casing may have a polygonal shape in a plan view, may have a circular shape, or may have an asymmetric shape with respect to the rotation axis.

The upper casing may not be necessarily provided. For example, a motor, a circuit board, and an impeller may be attached to the lower casing to form a centrifugal fan and the lower casing is directly fixed to another apparatus to mount the centrifugal fan on the apparatus.

The shape of the impeller is not limited to the above-mentioned shape. In the impeller, the parts on the outer circumference edge sides of both the lower surface of the annular shroud and the upper surface of the main plate may not be curved. The impeller is not limited to the structure in which the gap size in the axial direction between the annular shroud and the main plate gradually increases from the positions of the outer circumferential edges of the blades to the outer circumferential edge of the impeller. The diameter of the impeller may not be greater than the diameter of a circle passing through the outer circumferential edges of the blades.

The shape or position of the recessed portion formed in the impeller is not limited to the above-mentioned ones. That is, the position or shape of the recessed portion may be set to correspond to the positions or shapes of members mounted on the circuit board such that the members mounted on the circuit board and the impeller do not interfere with each other when the impeller rotates. Accordingly, it is possible to dispose the circuit board and the impeller to be close to each other and thus to decrease the thickness of the centrifugal fan.

It should be understood that the above-mentioned embodiment is exemplary in terms of all points of view but is not restrictive. The scope of the present invention is defined by the appended claims, not by the above description, and includes all modifications within a meaning and a scope of the claims. 

What is claimed is:
 1. A centrifiigal fan comprising: a motor; an impeller having an inlet port, the impeller being configured to be rotated by the motor and to discharge air suctioned from the inlet port outward from an outer circumferential portion of the impeller; a lower casing that is located below the impeller; a circuit board disposed between the lower casing and the impeller, the circuit board being mounted with an electrical component including a drive circuit that drives the motor, wherein the impeller has a recessed portion formed in an annular shape around a rotational axis and on a lower face that faces the lower casing and the circuit board, and wherein at least a part of the electrical component is located inside the recessed portion of the impeller.
 2. The centrifugal fan according to claim 1, wherein the lower casing is provided with an accommodating portion that is formed to concave downward, and wherein at least a part of the motor and at least a part of the circuit board are located inside the accommodating portion of the lower casing.
 3. The centrifugal fan according to claim 1, wherein the impeller has a hub connected to the motor, a main plate connected to the hub, an annular shroud, and a plurality of blades arranged between the main plate and the shroud, and wherein the recessed portion is formed on a lower face of the main plate that faces the lower casing and the circuit board.
 4. The centrifugal fan according to claim 3, wherein the impeller has a diameter that is greater than a diameter of a circle passing through an outermost circumferential edge of the blades, and wherein a gap size between the shroud and the main plate in an axial direction gradually is set to be enlarged from a position of the outermost circumferential edge of the blades toward an outer circumferential edge of the impeller.
 5. The centrifugal fan according to claim 4, wherein a part of one of a lower face of the of the shroud and an upper face of the main plate at the outer circumferential edge of the impeller is curved to form a wing upper surface shape.
 6. The centrifugal fan according to claim 4, wherein an upper face of the main plate at the outer circumferential edge of the impeller is curved. 